More than 800 people were injured on Sunday as riot police attacked peaceful protesters and unarmed civilians gathered to cast their ballots.
After the polls closed, Catalan president Carles Puigdemont said Catalonia had “won the right to become an independent state,” adding that he would keep his pledge to declare independence unilaterally from Spain if the “yes” side wins.
“Today the Spanish state wrote another shameful page in its history with Catalonia,” Puigdemont added, saying he would appeal to the European Union to look into alleged human rights violations during the vote.
Catalan regional government spokesman Jordi Turull told reporters that 90 per cent of the 2.26 million Catalans who voted chose the “yes” side in favour of independence.
He said nearly 8 per cent of voters rejected independence, while the rest of the ballots were blank or void. He said 15,000 votes were still being counted, and that the number of ballots didn’t include those confiscated by Spanish police during violent raids that aimed to stop the vote.
The region has 5.3 million registered voters.
No one knows precisely what will happen if Catalan officials actually follow through on their pledge to use the vote - chaotic as it was - as a basis for declaring the northeastern region independent.
Such a provocative move would threaten Spain with the possible loss of one of its most prosperous regions, including the popular coastal city of Barcelona, the regional capital.
Clashes broke out less than an hour after polls opened, and hundreds of police armed with truncheons and rubber bullets were sent in from other regions to confiscate ballots and stop the voting.
Amateur video showed some officers dragging people out of polling stations by the hair, throwing some down stairs, kicking them and pushing them to the ground.
Police were acting on a judge’s orders to stop the referendum, which the Spanish government had declared illegal and unconstitutional - and Prime Minister Mariano Rajoy said going forward with the vote only served to sow divisions.
In a televised address after the majority of polls closed Sunday, he thanked the Spanish police, saying they had acted with “firmness and serenity” - comments sure to anger Catalans.
Spanish Foreign Minister Alfonso Dastis said the violence, while “unfortunate” and “unpleasant” was “proportionate”.
“If people insist in disregarding the law and doing something that has been consistently declared illegal and unconstitutional, law enforcement officers need to uphold the law,” Dastis told The Associated Press.
By the end of the day, Catalan health services said 844 civilians had been treated in hospitals for injuries, including two who were in a serious condition and another person who was being treated for an eye injury that fit the profile of having been hit by a rubber bullet. Thirty-three police officers were also injured.
Catalans favouring a break with Spain have long wanted more than the limited autonomy they now enjoy, arguing that they contribute far more than they receive from the central government, which controls key areas including taxes and infrastructure.
There was no organised campaign for the “no” side in the vote, which most national political parties boycotted because it lacked legal guarantees and was suspended by the courts.
Polls in recent years have shown roughly half of the 7.5 million residents of the region want to remain a part of Spain.
Mari Martinez, a 43-year-old waitress, said she did not vote in Sunday’s referendum.
“I don’t lean toward independence, because we are part of Spain,” she said. “Today’s violence is not good for anybody. We never should have gotten to this point. Politicians haven’t done their job, and they should have reached an agreement a long time ago.”
Tensions were running so high that Barcelona played its football game against Las Palmas without fans after the team announced the match would be played behind closed doors.